It looks like you have mixed Managed C++ and C++/CLI syntax.
If you are using Managed C++ (not C++/CLI), the declaration of managed objects is different:
Managed C++ syntax:
String __gc *RptPath = S"whatever";
C++/CLI syntax:
String^ RptPath;
Note that Managed C++ is deprecated by now, so if possible, i would suggest using C++/CLI instead (it also has a clearer syntax).